Starship Asterisk*

http://marsrovers.nasa.gov/newsroom/pressreleases/20090810a.html wrote:
Meteorite Found on Mars Yield Clues About Planet's Past : August 10, 2009

This view of a rock called "Block Island," the largest meteorite yet found on Mars,
comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity

PASADENA, Calif. -- <<NASA's Mars Rover Opportunity is investigating a metallic meteorite the size of a large watermelon that is providing researchers more details about the Red Planet's environmental history.

The rock, dubbed "Block Island," is larger than any other known meteorite on Mars. Scientists calculate it is too massive to have hit the ground without disintegrating unless Mars had a much thicker atmosphere than it has now when the rock fell. Atmosphere slows the descent of meteorites. Additional studies also may provide clues about how weathering has affected the rock since it fell.

Two weeks ago, Opportunity had driven approximately 600 feet past the rock in a Mars region called Meridiani Planum. An image the rover had taken a few days earlier and stored was then transmitted back to Earth. The image showed the rock is approximately 2 feet in length, half that in height, and has a bluish tint that distinguishes it from other rocks in the area. The rover team decided to have Opportunity backtrack for a closer look, eventually touching Block Island with its robotic arm.

"There's no question that it is an iron-nickel meteorite," said Ralf Gellert of the University of Guelph in Ontario, Canada. Gellert is the lead scientist for the rover's alpha particle X-ray spectrometer, an instrument on the arm used for identifying key elements in an object. "We already investigated several spots that showed elemental variations on the surface. This might tell us if and how the metal was altered since it landed on Mars."

The microscopic imager on the arm revealed a distinctive triangular pattern in Block Island's surface texture, matching a pattern common in iron-nickel meteorites found on Earth.

"Normally this pattern is exposed when the meteorite is cut, polished and etched with acid," said Tim McCoy, a rover team member from the Smithsonian Institution in Washington. "Sometimes it shows up on the surface of meteorites that have been eroded by windblown sand in deserts, and that appears to be what we see with Block Island."

Opportunity found a smaller iron-nickel meteorite, called "Heat Shield Rock," in late 2004. At about a half ton or more, Block Island is roughly 10 times as massive as Heat Shield Rock and several times too big to have landed intact without more braking than today's Martian atmosphere could provide.

"Consideration of existing model results indicates a meteorite this size requires a thicker atmosphere," said rover team member Matt Golombek of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Either Mars has hidden reserves of carbon-dioxide ice that can supply large amounts of carbon-dioxide gas into the atmosphere during warm periods of more recent climate cycles, or Block Island fell billions of years ago."

Spectrometer observations have already identified variations in the composition of Block Island at different points on the rock's surface. The differences could result from interaction of the rock with the Martian environment, where the metal becomes more rusted from weathering with longer exposures to water vapor or liquid.

"We have lots of iron-nickel meteorites on Earth. We're using this meteorite as a way to study Mars," said Albert Yen, a rover team member at JPL. "Before we drive away from Block Island, we intend to examine more targets on this rock where the images show variations in color and texture. We're looking to see how extensively the rock surface has been altered, which helps us understand the history of the Martian climate since it fell."

When the investigation of Block Island concludes, the team plans to resume driving Opportunity on a route from Victoria Crater, which the rover explored for two years, toward the much larger Endeavour Crater. Opportunity has covered about one-fifth of the 12-mile route plotted for safe travel to Endeavour since the rover left Victoria nearly a year ago.>>

http://en.wikipedia.org/wiki/Block_Island wrote:
<<Block Island is part of the Outer Lands region, a coastal archipelago made by the recessional and terminal moraine that resulted from the Wisconsonian Laurentide glacier retreat, about 22,000 years before present. Block Island has been visited by presidents Bill Clinton and Ulysses S. Grant.



In 1524, what later became known as Block Island was sighted by Giovanni da Verrazzano, who named it "Luisa" after Louise of Savoy, the Queen Mother of France, and the mother of Francis I. However, several maps of the era named the island "Claudia," in honor of Claude, the wife of Francis I. Verrazano described Luisa (Claudia) as "about the size of the Island of Rhodes." In fact, they are shaped very similarly. When the founders of Colony of Rhode Island and Providence Plantations surveyed the land, they thought that Aquidneck Island was the place referred to by Verrazano—possibly because in 1614, it was charted by the Dutch explorer Adrian Block, after whom it is named. At the time of the arrival of the Europeans, it was occupied by a branch of the Narragansett people who called the island "Manisses" which means "island of the little God" in the language of the Narragansett tribe. English settlers from the mainland first arrived in 1661 led by Captain John Underhill, when the island was part of the Massachusetts Bay Colony. The island became part of the colony of Rhode Island in 1672 and the island government adopted the name "New Shoreham." A Dutch map of 1685 clearly shows Block Island, indicated as Adrian Block Island ("Adriaen Blocks Eylant").

In 1699 the Scottish sailor William Kidd visited Block Island, shortly before he was accused of piracy and hanged. At Block Island he was supplied by Mrs. Mercy (Sands) Raymond, daughter of the mariner James Sands. The story has it that, for her hospitality, Mrs. Raymond was bid to hold out her apron, into which Kidd threw gold and jewels until it was full. After her husband Joshua Raymond died, Mercy moved with her family to northern New London, Connecticut (later Montville), where she bought much land. The Raymond family was thus said to have been "enriched by the apron".

In 1829 the original North Lighthouse was built, but it was replaced in 1837 after it was washed out to sea. This lighthouse was also claimed by the ocean. In 1867, the lighthouse that can be seen today was constructed.>>

pacfandave wrote:A fallen meteor? And yet there is no crater and no surface material blown up around it. Perhaps it hit somewhere else and then rolled to its present location, the Martian wind having eradicated it's path.

http://www.astronomynow.com/090113Marsrocksareonthemove.html wrote:
Mars rocks are on the move
BY DR EMILY BALDWIN
ASTRONOMY NOW Posted: 09 January, 2009

<<Contrary to a previous explanation that suggested high speed winds were responsible for rolling rocks around the red planet, a new model shows that a much more ordered system transports rocks upwind.

Recent images taken by the Mars Exploration Rover Spirit show small rocks regularly spaced about five to seven centimetres apart, in organised patterns, on the plains between Lahontan Crater and the Columbia Hills. One previous explanation suggested that the rocks – some of which are as large as footballs – were picked up and carried downwind by winds reaching several hundred metres per second (at a height of two metres above the ground). This is much higher than wind speeds observed on Mars today, so the authors concluded that the patterns were created in a much windier Mars of the past.


The Spirit rover took these images of evenly space rocks on Mars. Image courtesy J. Pelletier, UA.

In a new study, Jon Pelletier, associate professor of geosciences at the University of Arizona, suggests that the wind works in a different way to slowly tease the rocks from one place to another. Moreover, Pelletier’s model sees the rocks moving upwind. "My model requires only enough wind to pick up sand, about 10-20 metres per second at two metre height," he tells Astronomy Now.

In his model, the wind blows sand away from the front of a rock, creating a pit, and deposits it behind the rock, creating a hill. The rock then rolls forward into the pit, moving into the wind. As long as the wind continues to blow, the process is repeated and the rocks edge forward.

"You get this happening five, 10, 20 times then you start to really move these things around. They can move many times their diameter,” says Pelletier. "In a wind tunnel it takes about 10 minutes [to move their own diametrer]. On Mars it would take about the same time if the wind was strong enough. Winds are variable, so it's hard to say exactly, but if the winds are moderately strong and steady, it takes very little time."


A schematic to explain how the rocks move upwind, by rolling into pits carved out by winds blowing across the Martain plains. Image courtesy J. Pelletier, UA.

The process is similar for rock clusters, too. However, rocks in the front of the group shield those in the middle or on the edges from the wind. Because the middle and outer rocks are not directly hit by the wind, the wind creates pits to the sides of those rocks. Therefore, they roll to the side, not directly into the wind, and the cluster begins to spread out.

The finding supports previous work that one of Pelletier’s study team members had conducted thirty years ago. James Steidtmann of the University of Wyoming had studied upwind migration by using a wind tunnel to see how pebbles on sand moved in the wind. Steidtmann's research showed that the rocks moved upwind and that over time, a regular pattern emerged.

To investigate the regular patterns of the rocks on Mars, Pelletier combined three standard numerical computer models to take into account air flow, erosion and the deposition of sand, and the rocks' movement. He also conducted what is known as a Monte Carlo simulation, which applies his model over and over to a random pattern of rocks to see how they ultimately end up. Out of 1,000 simulations the rocks formed a regular pattern 90 percent of the time. As an independent verification, he also compared the pattern predicted by the numerical model to the distances between each rock and its nearest neighbour in the Mars images, and found that they were well matched.


Simulations also predict the movement of rocks from an initially random configuration (left) into a more ordered pattern (right). Image courtesy J. Pelletier, UA.

Upward migration of rocks also occurs on Earth, but is difficult to study due to interference from plants, wildlife and humans. Pelletier says that this migration could still be observed on Mars today. "If a current or future rover took images of the same location with a time span of a significant wind storm, it could be observed," he says. "The only caveat is that once the rocks develop a more ordered pattern (from a random initial one) they do not rearrange as often."

The work is reported in the January issue of the journal Geology>>

Alicia wrote:If the rock found on Mars dubbed Block Island is a meteorite, Where is the crater?

orin stepanek wrote:Thanks Art for the color view of Block Island Meteorite! I'm amazed at the impact craters on the small meteorite.
Or are they the result of intense heat during the formation of the rock. What a story it could tell.

http://en.wikipedia.org/wiki/Willamette_Meteorite wrote:
Willamette Meteorite at the American Museum of Natural History
Iron : IIIAB : Medium Octahedrite
7.62% Ni, 18.6ppm Ga, 37.3ppm Ge, 4.7ppm Ir
Total Known Weight (TKW) 14150 kg



<<The Willamette Meteorite, officially named Willamette, is an iron-nickel meteorite discovered in the U.S. state of Oregon. It is the largest meteorite found in the United States and the sixth largest in the world. No impact crater was preserved at the discovery site; it is possible that the meteorite landed in what is now Canada and was transported to where it was found by moving ice sheets. It is currently on display at the American Museum of Natural History.

The Willamette Meteorite weighs about 32,000 pounds or 15.5 tons. It is classified as a type III iron meteorite, being composed of over 91% iron and 7.62% nickel, with traces of cobalt and phosphorus. The approximate dimensions of the meteorite are 10 feet (3.05 m) tall by 6.5 feet (1.98 m) wide by 4.25 feet (1.3 m) deep.

The distinctive pitting on the surface of the meteorite is believed to have resulted from both its high-speed atmospheric entry and subsequent weathering. In the case of weathering, rainwater interacted with the mineral troilite, resulting in a form of sulfuric acid which slowly dissolved portions of the meteorite. This resulted (over a very long period) in many of the pits that are visible today. Willamette has a recrystallized structure with only traces of a medium Widmanstätten pattern, it is the result of a significant impact-heating event on the parent body.
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http://en.wikipedia.org/wiki/Canyon_Diablo_(meteorite) wrote:
The young 50,000 year old Canyon Diablo meteorite
7.1% Ni; 1% S; 1% C; 0.46% Co; 0.26% P; 320ppm Ge; 80ppm Ga; 1.9ppm Ir

.........................................................................

http://en.wikipedia.org/wiki/Pyrrhotite wrote:
<<Pyrrhotite is an unusual iron sulfide mineral with a variable iron content: Fe(1-x)S (x = 0 to 0.2). The FeS endmember is known as troilite. Pyrrhotite is also called magnetic pyrite because the color is similar to pyrite and it is weakly magnetic. Pure troilite is non-magnetic. Troilite is rarely found as a native mineral on Earth, but is abundant in meteorites, in particular those originating from the Moon and Mars. Uniform presence of troilite on the Moon and possibly on Mars has been confirmed by the Apollo, Viking and Phobos space probes. The relative intensities of isotopes of sulfur are rather constant in meteorites as compared to the Earth minerals, and therefore troilite from Canyon Diablo meteorite is chosen as the international sulfur isotope ratio standard. Troilite is named after Italian abbot Domenico Troili who first noted the mineral in a meteorite that fell in 1766 at Albareto, Modena (Italy). Troili wrote the first description of the fall of a meteorite in a 43-page document published in 1766. He collected reports from many eyewitnesses, closely examined the stone and detected in it small grains of a brassy mineral he called "marchesita", which was long assumed to be pyrite, FeS2. However, in 1862, German mineralogist Gustav Rose analyzed the composition and determined it as FeS. Rose named this new mineral troilite after Troili.>>

-------------------------------------------------------
Modern history

The Willamette Meteorite was discovered in the Willamette Valley of Oregon near the modern city of West Linn. Although apparently known to Native Americans, its modern discovery was made by settler Ellis Hughes in 1902. At that time the land was owned by the Oregon Iron and Steel Company. Hughes recognized the meteorite's significance, and in an attempt to claim ownership, secretly moved it to his own land. This involved 90 days of hard work to cover the 3/4 mile (1200 m) distance. The move was discovered, and after a lawsuit, the Oregon Supreme Court held that Oregon Iron and Steel Company was the legal owner. Oregon Iron Co. v. Hughes, 47 Or 313, 82 P 572 (1905).



In 1905 the meteorite was purchased by Mrs. William E. Dodge for $26,000. After being displayed at the Lewis and Clark Centennial Exposition, it was donated to the American Museum of Natural History in New York City where it is now on display.

The meteorite was an object venerated by the Native American tribe inhabiting the area where it was found. The Confederated Tribes of the Grand Ronde Community of Oregon, a confederation of Native American tribes, used the meteorite, which they call Tomanowos, in an annual ceremony, and have requested that it be returned. The tribes reached an agreement with the museum in 2000. This states that tribal members may conduct a private ceremony around the meteorite once a year, and that ownership will be transferred to them should the museum stop using it for display.>>

http://en.wikipedia.org/wiki/Endeavour_(crater) wrote:
<<Endeavour is an impact crater located in Meridiani Planum on Mars. Since August of 2008, Mars Exploration Rover-B Opportunity has been travelling towards it. Endeavour is 22 kilometers (13.70 miles) in diameter which compares to Victoria crater which is 750 meters (.47 miles), Endurance crater which is 130 meters (.08 miles), and Eagle crater which is 22 meters (.01 miles). Based on the amount of time it had taken to drive from Victoria it was estimated that it would take over one Martian year (23 months) for Opportunity to reach Endeavour.>>

• Crater ________ Diameter in meters
  --------------------------------------------------------------
  Aitken ___________ 2,500,000
  Turgis_____________ 580,000
  Schiaparelli________ 460,000
  Chicxulub _________ 170,000
  Endeavour __________22,000
  Barringer ___________ 1,200
  Victoria ______________ 750
  Endurance ____________130
  Eagle _________________ 22

neufer wrote:

http://en.wikipedia.org/wiki/Endeavour_(crater) wrote:<<Endeavour is an impact crater located in Meridiani Planum on Mars. Since August of 2008, Mars Exploration Rover-B Opportunity has been travelling towards it. Endeavour is 22 kilometers (13.70 miles) in diameter which compares to Victoria crater which is 750 meters (.47 miles), Endurance crater which is 130 meters (.08 miles), and Eagle crater which is 22 meters (.01 miles). Based on the amount of time it had taken to drive from Victoria it was estimated that it would take over one Martian year (23 months) for Opportunity to reach Endeavour.>>

• Crater ________ Diameter in meters
  --------------------------------------------------------------
  Chicxulub _________ 170,000
  Endeavour __________22,000
  Barringer ___________ 1,200
  Victoria ______________ 750
  Endurance ____________130
  Eagle _________________ 22

rstevenson wrote:You folks exhibit a paucity of imagination. Think long time scale; think tens of millions of years, perhaps as much as a billion.

Imagine the rock reaching, as they said, terminal velocity and then falling into a large, thick sand dune, or maybe a deep mud puddle if Mars happened to be wetter then. Then imagine it gradually settling down as the surrounding materials erode away, first perhaps through water erosion, then later through wind erosion. Given this scenario there is little likelihood we'd see any trace of an impact crater even if one had been created originally.

As for the white rocks shown nearby, they're in evidence in many of the photos from Endeavor, and have been discussed (elsewhere if not here) at great length. You could have a look here for more info... http://marsrovers.jpl.nasa.gov/mission/ ... tyAll.html

smita wrote:Could someone please tell me what are the white (lighter-shade) patches around Block Island?

Thanks.

BMAONE23 wrote:Given the Iron content, I would think that the remainder would be rusty colored
if it sat in a moist environment or fell onto wet mud.

• The atmosphere on Mars consists of
  95% carbon dioxide,
  3% nitrogen,
  1.6% argon, and
  traces of oxygen & water.

bsk wrote:could somebody tell me why there is no hole/crater under the block (meteorite) shown on the picture? Surely the block when it hit Mars should have produce a hole?

thanks
BSK

Alicia wrote:Hello
If the rock found on Mars dubbed Block Island is a meteorite, Where is the crater?
Thank you.

Alicia

pacfandave wrote:A fallen meteor? And yet there is no crater and no surface material blown up around it. Perhaps it hit somewhere else and then rolled to its present location, the Martian wind having eradicated it's path.

janndave wrote:When I looked at the picture today on the site I couldn't figure out where the divot was from the meteorite landing Mars. What's the deal? Help!

nealgalt wrote:I wonder why there is no evidense of impact in the photo...crater, etc. The meteorite is on top of the soil.???????? Neal

http://www.planetary.org/blog/article/00002050/ wrote:
________ Opportunity & Block Island


<<The HiRISE image of Victoria crater taken on July 19, 2009 also included the Mars Exploration Rover Opportunity (left) and the meteorite it would soon backtrack to study, Block Island (right). Credit: NASA / JPL / UA>>

neufer wrote:

BMAONE23 wrote:Given the Iron content, I would think that the remainder would be rusty colored
if it sat in a moist environment or fell onto wet mud.

One also needs oxygen to rust.
(Rust on Earth is mostly the fault of plant life not water.)

• The atmosphere on Mars consists of
  95% carbon dioxide,
  3% nitrogen,
  1.6% argon, and
  traces of oxygen & water.